Sure, there will be an initial boost -- mostly conservatives who are suspicious of or outright dislike Romney, coming back into the fold, along with some fiscally conservative independents who don't know any better -- but it won't last. As Charles Pierce wrote:

Paul Ryan is an authentically dangerous zealot. He does not want to
reform entitlements. He wants to eliminate them. He wants to eliminate
them because he doesn't believe they are a legitimate function of
government. He is a smiling, aw-shucks murderer of opportunity, a
creator of dystopias in which he never will have to live. This now is an
argument not over what kind of political commonwealth we will have, but
rather whether or not we will have one at all, because Paul Ryan does
not believe in the most primary institution of that commonwealth: our
government. The first three words of the Preamble to the Constitution
make a lie out of every speech he's ever given. He looks at the country
and sees its government as something alien that is holding down the
individual entrepreneurial genius of 200 million people, and not as
their creation, and the vehicle through which that genius can be
channelled for the general welfare.

So why did Romney pick such an extremist?

In his decision to make Paul Ryan, the zombie-eyed granny-starver from
Wisconsin, his running mate, Romney finally surrendered the tattered
remnants of his soul not only to the extreme base of his party, but also
to extremist economic policies, and to an extremist view of the country
he seeks to lead...

Which is not to say this isn't a shrewd move. In one great swoop,
Willard has recaptured a good portion of the elite political media,
which has been crushing on Ryan's "courage" to take on the "tough
choices" — none of which, it should be pointed out, likely will affect
Ryan, who's already got himself an education out of the social safety
net he now intends to shred, and certainly will never affect the haircut
at the top of the ticket, or his great-grandchildren, for all that —
and the coverage of the pick in the middle of the night showed that many
of our finer chattering heads are already practicing tying the stem of
the cherry with their tongues in preparation for covering the new
Republican ticket.

Brilliantly put. Falling in the polls and coming off a disastrous foreign tour, Romney needed... yes, I'm going there... to change the game. He has been touting himself all along as the guy with the business chops to get the economy moving again, his main selling point being that Obama hasn't done enough. But that wasn't working anymore. Voters don't think he'd improve the economy any more than Obama would in a second term, and increasingly he was coming across as a gaffe-prone embarrassment with no foreign policy experience, the character of a privileged rich douchebag, and a lot to hide, mostly in his tax returns. To have any realistic shot at winning in November, he needed to win back the national media, which had begun to treat him as a joke (and which had slowly come to see him as he really is, in large part a result of extremely effective work by the Obama campaign to define him as an out-of-touch, and worse, plutocrat), and conservatives, who had flocked to him in partisan lock step when he wrapped up the nomination despite their massive reservations but who had begun to turn on him.

With Ryan -- a conservative and media darling -- he seeks to do just that.

But did he really want to pick Ryan? I suspect not. Or, at least, not until just recently.

As it is, Romney can try to market himself as a business-savvy
pragmatist who can get the economy moving again, which is what he's been
doing. But if he's got Ryan with him, then it's not about fixing the
economy, it's about implementing a far-right agenda that includes
Medicare privatization and other deeply unpopular (with the electorate
at large, if hugely popular with conservatives) initiatives. It will be
hard for Romney to make the case that he's the one to trust with the
economy, offering up vague proposals in the hope that voters take a
chance on him, if the debate turns into a referendum not on Obama's
handling of the economy but on Ryan's budget plan, which, after all, has
become Republican orthodoxy.

Romney's entire plan for victory hinges on lying about Obama, making vague claims about what he'd do as president (he's been something of a Keynesian in the past, but more recently he's been pandering to the anti-government right and stressing tax cuts, mostly for the rich), and hoping the economy is in bad enough shape that swing-state independents and undecideds give him a shot.

But Ryan is all about, or mostly about, the details. It's Medicare privatization and other such unpopular initiatives, but it's also, as Pierce suggests, the undoing of the social compact altogether. It's basically the imposition of Ayn Rand on America.

Does Romney really want that? Probably not. He's a plutocrat, to be sure, but his history is more about right-leaning pragmatism than right-wing ideology. And so I suspect he would have preferred someone like Tim Pawlenty or Rob Portman, two conservative but by no means absolutist midwesterners with whom he seems to have a great rapport. Or perhaps the very similar Mitch Daniels. Or perhaps Bobby Jindal, a conservative but also a state executive who certainly has a better understanding of how the world works than Any Rand's disciple in Washington. Or perhaps, and perhaps ideally, Chris Christie, who would have complemented him so nicely.

But, no, it's Ryan, and it's Ryan because of conservatives and circumstances. If this had been even just a couple of weeks ago, he may have gone in a different direction. More than that and he almost certainly would have, back when he was running even with the president in the polls and when it looked like the struggling economy would keep him there. Back then, he would have made a choice that would have stressed his own bona fides, a choice to reassure voters that he was serious about trying to fix the economy. Again: Pawlenty or Portman.

But he's desperate now, and, like McCain, he needed a game changer.

No, no, we won't see that desperation, and of course all we're hearing now is how great this pick is, as if it was meant to be. But there no other reason to pick Ryan than desperation -- the deperate need to change the story, the dominant campaign narratives, the need to solidify and perhaps even expand conservative support and to have the media take him seriously again.

In this sense, my argument is much the same as Nate Silver's, among others:

When is it rational to take a big risk?

When the status quo
isn't proceeding in a way that you feel is favorable. When you have less
to lose. When you need — pardon the cliché, but it's appropriate here — a "game change."

There you go. I'm not alone in using the "game change" reference. Silver also notes that there were other "bold" picks Romney could have made without taking such an enormous risk, such as Christie and Marco Rubio, both of whom I had in my Romney Veepstakes Final Four.

And why is it such a risk? Because, again, he's a right-wing extremist who isn't at all shy about his extremism -- and because what he stands for, what he wants to do, is massively unpopular with the American people, however much it may make conservatives drool. And because Romney is obviously conceding that Ryan is the real leader of the Republican Party, as Jon Chait writes:

Romney has made the risky but defensible calculation that, if he is to
concur with most of his party's ideological baggage, he might as well
bring aboard its best salesman...

Ryan's nomination represents
an important historical marker and the completion of a 50-year struggle.
Starting in the early sixties, conservative activists set out to seize
control of the Republican Party. At the time the party was firmly in the
hands of Establishmentarians who had made their peace with the New
Deal, but the activists regarded the entire development of the modern
regulatory and welfare states as a horrific assault on freedom bound to
lead to imminent societal collapse. In fits and starts, the
conservatives slowly advanced – nominating Goldwater, retreating under
Nixon, nominating Reagan, retreating as Reagan sought to govern, and on
and on through Gingrich, Bush, and his successors.

Over time the movement and the party have grown synonymous, and
Ryan's nominations represents a moment when the conservative movement
ceased to control the politicians from behind the scenes and openly
assumed the mantle of power.

In other words, the Ryan pick dramatically changes the entire focus of this race. It will no longer be about the supposedly business-savvy outsider challenging the supposedly ineffectual (or dangerously radical, if you buy the right-wing bullshit) incumbent. It will be about the policy agenda of Paul Ryan's (and, in a sense, Ayn Rand's) Republican Party, and about its ongoing assault on the social compact, on the very foundations of American democratic self-governance.

And the thing is, that policy agenda is incredibly unpopular. (Is it any wonder the Obama campaign is happy about this pick, even if it means an initial boost for Romney? Instead of going against Romney's vagueness, defining him as a plutocrat and hoping to tie him to right-wing extremism, they now face a ticket that includes the enthusiastic engineer of that extremism.)

Did Romney have to do this? Yes, perhaps. A Pawlenty or a Portman just wasn't going to cut it. But I can't imagine he's really all that happy about it.

Perhaps he gave himself a better shot at winning in November, if everything were to go just right, but he's tuned this election into a referendum not so much on Obama but on the Republican Party. And in that there is, both for him and the party, the prospect of disaster.